You can find the main ideas by looking at the way in which paragraphs are written:

A paragraph is a group of sentences about one main idea.

Paragraphs usually have 2 types of sentences:

------a topic sentence, which contains the main idea,
and
------one or more detail sentences which support, prove, provide more information, explain, or give examples.

You can only tell if you have a detail or topic sentence by comparing the sentences with each other. The only exception to this is if there is only one sentence in the paragraph. Then the one sentence is the topic sentence.

Look at this example paragraph:

There are many uses for this great product. ---TOPIC SENTENCE

Some mix it with chocolate to make cake icing. --DETAIL SENTENCE

It is the main ingredient in some milkshake mixes. --DETAIL SENTENCE

It will also kill rats in small amounts. --DETAIL SENTENCE

The first sentence introduces the main idea and the other sentences support and give the many uses for the product.

Rules for Finding the Topic Sentence

1. The topic sentence is usually first, but could be in any position in the paragraph.

2. A topic is usually more "general" than the other sentences, that is, it talks about many things and looks at the big picture. Sometimes it refers to more that one thing. Plurals and the words "many", "numerous", or "several" often signal a topic sentence.

3. Detail sentences are usually more "specific" than the topic, that is, they usually talk about one single or small part or side of an idea. Also, the words "for example", "i.e.", "that is", "first", "second", "third", etc., and "finally" often signal a detail.

4. Most of the detail sentences support, give examples, prove, talk about, or point toward the topic in some way.

How can you be sure that you have a topic sentence? Try this trick:

---Switch the sentence around into a question. If the other sentences seem to "answer" the question, then you've got it.